A disk drive is an information storage device. The most basic parts of a disk drive are an information storage disk that is rotated, an actuator that moves a slider carrying one or more transducers to various locations over the disk, and electrical circuitry that is used to write and read data to and from the disk. The one or more information storage disks are clamped to a rotating spindle. More specifically, storing data includes writing information representing the data to portions of tracks on a disk. The transducer includes two separate devices—a write transducer that writes information representing data to the disk and a read transducer or sensor that reads information from the disk.
The slider is a small ceramic block that carries the one or more transducers. The slider is aerodynamically designed so that it flies over the disk. The slider is passed over the disk in a transducing relationship with the disk. Most sliders have an air-bearing surface (“ABS”) which includes rails and a cavity between the rails. When the disk rotates, air is dragged between the rails and the disk surface causing pressure, which forces the head away from the disk. At the same time, the air rushing past the cavity or depression in the air bearing surface produces a negative pressure area. The negative pressure or suction counteracts the pressure produced at the rails. The slider is also attached to a load spring which produces a force on the slider directed toward the information disk surface. The various forces equilibrate so the slider flies over the surface of the information disk at a particular desired fly height. The fly height is the distance between the information disk surface and the one or more transducing heads, which is typically the combined thickness of the air gap and lubricant film. This film eliminates the friction and resulting wear that would occur if the transducing head and disk were in mechanical contact during disk rotation.
Data retrieval includes reading the information representing data from the portion of the track on which the information representing data was stored. The read transducer or sensor is housed within a slider which is flown or passed over the disk at a height where the transducer can read information from the disk. The slider is attached to actuator. The actuator positions the read sensor or transducer over a track having the desired information. The actuator rotates the slider and read sensor or transducer over the track containing the desired information, in another embodiment, the actuator is moved linearly. A voice coil motor drives the actuator.
The disk drive also includes circuitry for encoding data so that it can be successfully written to the disk surface, and subsequently decoding the information retrieved from the disk so that the information can be replicated. A microprocessor controls most of the operations of the disk drive as well as passing the data back to the requesting computer and taking data from a requesting computer for storing to the disk. The electronics used to encode and write information representing data, and to decode the read information is generally referred to as the read/write channel.
There are many types of read sensors or transducers. These may also be referred to as read elements. In the past, there were metal in gap heads. More recently, the read sensors have been separate from the write transducers. The types of read sensors more common these days are magneto resistive (MR) sensors, tunneling magneto resistive (TMR) sensors, and giant magneto resistive (GMR) sensors.
The most common type of write transducer is a thin film head. These can be formed on a wafer using semiconductor process techniques. In many instances, the read elements can also be formed using semiconductor process techniques. In many instances, the write transducer is formed on a first layer and the read element is formed on another layer on top of the wafer. The wafer is diced and further processed to form the slider which carries the read transducer and the write transducer.